Telephone-exchange system.



TELEPHONE EXCHANGE SYSTEM. `.innemen'ION rum'oomejlso. R;NBwBD.J-AN.22,1912. 1,126,803.

Patented Feb. 2

I 6 SHEETS-SHEET 3.

.www5 mTmL F'. R.- MbBERTY. 4 Y TELEPHONE EXCHANGE SYSTEMlv A 4MPLIGATIQN :FILED 0012.6,19oe-` RENBWED JAN, 22. 1912. y ,1263803.`

Patented, Fabia- 1915. Ae SHEETS-SHEET 4.1

'and State of annulations-ausweiten Application filed October c, .1368, teria! 33o.

To all whom it 'may 'concern Be it known that I, FRANK lrdonnrr, citizen of the United States, residing at N ew Rochelle, in the county of Westchester New York, have invented 'a certain `new and useful lmprtWenfiei-it in Telephone-Exchange Systems, of which the following' is a full,'dlear, concise, and exact description.

lThis invention relates to a telephone exchange system, and its object is in general to provide an improved organization of apparatus and circuits whereby connections between subscribers lines may be made with v rapidity and certainty, :by automatic switching. mechanism which is companatively simple and inexpensive, and which does not require complicated controlling circuits nor especial care' in manipulation, the telephone transmission circuits and signaling circuits being of standard character, and the line be ing supplied with current from a voei'itral battery, as required by modern operating conditions.

Some of the features to be claimed in this application relate to an improved system or" Y control for the automatic switching niechanism including a novel form of controlling or sending apparatus by which a sequence of selecting operations may be brought about with great rapidity and accuracy. @ther features to be claimed relate to automatic means for controlling the association of the sending apparatus with the operators connecting circuits, establishing in the required l sequence the various circuits governing the operative relation of the selector mechanism to the sender apparatus and to the connecting-circuits and subscribers lines, establishing telephonie tiansinissioli-circuits of standard character as recognized by the best en-- gineering practice, supervising and controlling connections, and restoring the apparatus and circuits to normal condition after use.

Some features of the invention will be applicable to systems of the purely automatic type, in which the selectors are controlled by apparatus at the subscribers stations; but in the system to which l particularly contemplate applying the invention, it is intended that operators shall be stationed at a central olhce ol the telephone exchange, as in the manual system, to ansiver calls from subscribers and to cont rol and supervise the establishment of connections, the actual line- .LA o

@oriented lelor,

:January 22, 1912. Serial No. f

svvitcliii'ig operations, however, being perfortified by mechanical selectors; underthe electrical control of automatic sending if patatas which is brought into action by the operator. this system a number connetting circuits will be provided for the use oifveafch operator in funi-ting lines, each such, connecting ycircuit having means for itat ene end with a calling line, and terminating at the 4otheuend in a mechanical selector switch; means being provided temporarily associating with each connecting circuit the sending apparatus to con-Iv trol, in accordance with this invention, the action of suchselector and of the succeeding .selectors by and through which the circuit is successively extended from the callingf line to the line Wanted. Vifhen the connection is completed, the sending apparatus vvill be autornatically disconnected from the circuit been established, leaving it free. the sending paratus being then free to serre another con-` ivhidh has for telephone transmission,

necting circuit Iestablishing another conneotio ln accordance with the presentl invention,

the sending apparatus its governed by a barili or set of numeral keys which may be similar in arrangement to those of an chine, and

may be set in the combinations required to represent any line anism is combination of keys, to cause thereby to the line so designated. ln this uniting adding nia-` fnuniber ofthe system ;'and automatic controlling mech adapted, under contl'hlof l.any suchl series of op-` erati-ons of the selective line-switching 1nechanism such that the circuit will be extended system, therefore, the subscriber may transf mit a call in the usual Way and give his order tolthe operator; and thc operator upon learning the number of the line wanted vvill simply depress a combination of keys representingthis number, and this `\vill resi: fin the immediate selection of such Wanted line.

lhe sending apparatus includes a novice- Which may be termed a point-findeny adapted to traverse a series oi points which may be selected by the keys. Means are provided for setting the point finder in operation by the depression ot a key, under control of a stopping device which will be actuated vwhen the point selected by such key has been reached. The extent of travel of the pointi'inder in reaching the selected point measures the selecting operation of a distant niechanical switch or selector, a movable ele ment whereof 1s advanced 1n unison with the point-finder by means of'pulsations ofl current, each pulsation causing or corresponding to a unit of advance of both the selector and point-finder. When the stopping device is actuated by the point-inder 1n its predetermined limit of travel, the selecting operation is brought to an end, as by an automatic switch opening the controlling circuit which has been established between lthe selector and point-linden As each pointfmding operation is completed, automatic switching mechanism is brought into action prepare the circuits for another selecion; and one selector after another in the train through which the circuit is extended an automatic sequence-switching mechanism associated with the sending apparatus. rlhe selectors are also provided with local con; trollm apparatus for governing certaln 1ndepen( ent operations such as those of hunting idle'trunlts, and the sending apparatus is arran ed to suspend its action while such indepen `ent operations are taking place at the selectors. l

The invention includes various details of circuits and apparatus by which the operations above outlined, and other incidental operations, are brought about. .In developing a system of the type described, I have made a series of inventions relating to dif ferent parts of the complete organization, which inventions are more or less intimately related to one another, but are none the less distinct in themselves, and are available for use quite, independently in other systems. I prefer,"llowever, to illustrate and describe this invention in its application to the cour plete system for which it was particularly y worked out, containing many features which are the subject of other applications here after recited. In describing this system it will be necessary in the interest of clearness to set forth specifically and in detail the characteristics and mode ol operation kof the articular apparatus and clrcuits shown; but it will be understood that I do not intend such specific descriptive language to be taken as a precise definition of the limits of this invention; the parte,improvements or combinations which are intended to be covered herein being set forth in more general language 1n the claims. A t almost every point 1n the system minor modilicatious may be made in the apparatus and circuits ernployed, to effect the same results by equivalent electrical or mechanical means, without departing from the essential principles herein disclosed. For the purpose of illustration the system has been shown in the drawings as designed for a small exchange of one thousand lines capacity, but it will Y1n fact be particularly adapted for use in'large cities where each exchange may comprise, for example, ten thousand lines, alarge number of such exchanges being connected by inter-office trunk lines. The system may be expanded to provide for automatically connecting any line of such a large exchange with any line of another exchange, through a train of suitable selectors and trunk lines.

In the drawings, Figures 1, 2, 3 and 4 when placed together, edge to edge, in the order named, (Figs. 2, v3 and 4 being placed side by side, and Fig. 1 placed above Fig. 2) form a complete diagram, the lines which continue to the edge of each sheet being continued on neighboring sheets; the whole illustrating the circuits and apparatus involved in extending a connection from a calling line to a line called fof. Fig. l represents a bank of keys arranged in three sets, representing hundreds, tens and units digits, respectively. Fig. E2 represents one form of controlling or sending apparatus adapted to governy the various selecting operations, under control of the key shown in Fig. 1. Fig. 3 represents the calling subscribers line and the operators connecting circuit, together with the first selector forming the terminal of such connecting circuit, this being, in the small exchange illustrated, a hundreds selector; Fig. 4 represents the final selector Ito which the circuit may be extended by the first selector, and also represents the called line to which the final selector may make direct connection; Fig. 5 is a front view of one of the sequence-switches which are em )loycd in association with the selectors, an also in association with the sending apparatus, to establish in sequence the operating circuits forthe various parts; Fig. 6 is a side view of the sequence-switch; Fig. 7 is a detail sectional view on line 7-7 of Fig. 6; Fig. 8 is a sectional plan View on line 8-8 of Fig. 6.

The same reference-figures indicate corresponding parts wherever shown.

General plan of systeme-Then any one of the operators connecting circuits is put into service to answer a call, the sending apparatus is automatically appropriated to the use of that connecting circuit; and a controlling or stepping circuit is established between a controlling'relay at the first selector and a magnet at the sender which is adapted to operate a step-by-step mechanism. Means are provided for transinitting electrical impulses over this stepping y same Way.

, under control Licence,

circuit, and for operating the selector and the stepping mechanism at the sender in unisontherewith. The advance of the stepping Axn'e'ehanisr'n'at the sender in unison with the impulses transmitted over the stepping circuit furnishes a means for measuring ofi at the sender the exact extent of operation et the ldistant selector; and when a predetermined number of impulses have been trans` mitted, as indicated by the advance of the sender stepping mechanism to a predetermined point, the stepping circuit may be automatically opened, bringing that particular selecting operation to an end, after which another selection may be made in the Each selector in the train through which the circuit is successively eX- tended will, as it is reached, be brought l of the sending apparatus by the establishment of the selecting circuit, which includes a controlling relay or magnet at the selector and a relay or magnet at the sender adapted to operate the stepping mechanism thereof.

The extent of advance of the sender stepping mechanism is determined by the selection of one of a series of lterminals or points over which a point-finder lis advanced by the stepping mechanism, the particular points required for determining the successive selecting o crations being chosen by keys which are epressed by the operator. In the particular system shown,

designed for a thousand-line exchange, there are three i'owsiof tenke s each, nurnbered from 0 to 9 inclusive, one'row representing hundreds, another tens and the third units digits; and in this system there are three selecting operations, controlled respectively by the keys representing the three digits of the number of the line to be selected. The point-finder apparatus comprises a finder brush arranged to be advanced over a series of terminals-.by 'the stepping mechanism or escapement operated by the stepping magnet which resp'onds in unison With the stepping impulses; and the terminals are in three divisions, lthose in the first division being connected to contacts of corresponding hundreds keys, those in the second division to contacts of corresponding tens keys and those in the third division to contacts of corresponding units keys. Each key is adapted vhen depressed to select a corresponding terminalin .the present case by connecting such terminal to ground-and the finder brush upon reaching the terminal so selected will `complete a circuit for a stop relay. This relay in its response breaks the @uit over which the stepping impulses are'transmittcd. so bringing the selectingr operation to :in end. The response of the stop relay also brings switching mechanism ymechanism operated or tion has been made, whereupon the stop and so on until the last selecrelay in its response causes switching mechanism to be actuated which will disconnect the sending apparatus from the circuit which has been established, leaving the calling line united through the operators connecting cirduit and the train of selectors to the line which has been selected. In the system shown, the impulses for measuring each selection are derived from a battery associated4 with the selector under control, and are produced by the action of interruptorcontacts closed periodically in the advance of such selector, which intermittently shortcircuit the line. Power is applied to the movable element of the selector under control of a line relay, which is in a portion of the stepping circuit not shunted by the interrupter, and which is released when the circuit isopened by the stoprelay at the sender.

The local controlling-circuits at each selector and at the sending apparatus, which must be established in definite order at successive stages of the operation to bring intoy service different devices or parts as required, are in the present system established by automatic switching appliances which I term sequence-switches. There is a sequenceswitch for each selector, and 011e for the sending apparatus. Thesequence-switch consist-s in its elements of a movable switchoperating member, a number of circuitchangers or switches actuated in sequence as said member is moved from one position to another, an electromagnet, and motor controlled by said magnet .for advancing said movable member. The sequence-switch may control any desired sequence of operations, whether of the same or of different devices. In each position to which its movable member is advanced a circuit is established whereby a given operation of the device under control is made possible, and at the same time an# other circuit is established, whereby the inotor magnet of the sequence-switch may be actuated automatically when such operation of the device under control has been completed; so that as each operation takes place, the serpeence-svvitch will'beI autolnaticall lla'V advanced to the next position, in which a` tially as shown and described in my previous application., Serial No. l18,123, filed February 27, 1908; but an understanding of their general features of construction and mode of operation may be had by reference to the dia rams herein. Each selector has a rotary sliaft 50, carrying a. frame G0 at the outer end of which a. number of contact brushes 51, 52, 53, are pivoted in posi tion to travel over contact terminals 61, (32,'

63, mounted in rows concentric with the shaft. Spring tongues 54:, 55, 5G, extending from insulated metal. plates 41, 42, 43., re s ectively, press against projecting arms of tlie brushes, and besides making electrical connection therewith, tend to 'rock the brushes on their pivots in a direction to throw their forwarder contact ends out- Wardly. The brushes are arranged in sets of three. Corresponding brushes in each set are electrically connected in multiph` by means of metal plates 41, dit, 43, from which extend the spring tongiiies 5ft, 5G, and each set is normally latohed a gainst the r thrust of the spring tongues '34, 56, bv acatch 57 which is normally held in the path of movement of the rear ends of said brushes. .As shown, the catches 57 are insulating bars mounted on spring latch-arms 58, which are the free ends or tonglles of a spring metal plate 59 ixed te the rotary .frame (l0. In order to bring any set of brushes into position. to enOage the contacts over which they travel, tliey must be released by tripping the corresponding catch 57 to allow the brushes to be rocked upon their pivots by their springs 5 4, 55, 56. This tripping of the brushes is acconr plished by a trip-bar (il which is pivotally mounted on an axis 65 and has at its edge a series of projectingr lugs GG in position to be moved into the paths of the respective latch-arms 58 when the tripbar is rocked on its axis.

It is intended that only one of the sere `al sets of brushes shall be selected and tripped. in a given operation, and the trip-bar is therefore inclined at an angle so that the tripping lugs will face positions successively reached in the rotation oit the brusli-carrier frame. The trip-bar will he actuated to thrust forward its tripping lugs only for a moment when the end ot the latch-arm controlling the desired set of brushes reaches an angular position justin advance ol. that occupied by the particular lug which at the proper height to engage that arm. The movement of the trip-bar may 'oe accomplished by a tripping-magnet GT, the Inovable armature (S8 whereof is mechanically connected to said bar.

A segmental metallic plate is mounted in position to be engaged by the contact ends of the brushes as they are tripped., this plate extending to the end of the trip range llthat is, through the are traif'ersed by the brushes as one set :lit .1' another tln'ough ,\ut the series is brought into ).)osition to be tripped. At the end of the tr p range the" bank of line terininals (il, 62, 63, begins. These terminals are arranged, in sets ot' three, corresponding in relativo positions to Ythe relative positions of the brin-thas by which they are to be traversed, and the different sets are arranged in an are in position to be successively reached in ay point-topoint rotary advance of the brushes To restore the brushes to their latehed position when the selector returns to normal, an insulating bar 95 is arrangeil to be passed over by thc brushes in their return journey, the brushes in passing over this bar being raisedv thereby against the' tension i their springs, until. their beveled rear ends slip over the catches 57. i

The motor mechanism for rotating the brush carrier traine may he as 'folleuvsz An. iron plato 73 is .mounted to ro ite with the shaft 50, but in such manner tlf-Lat it .may be given a llatuvise or tilting nio uncut into engagement with one or the otlf iron friction-driving .rollers '74 are located on either side ot' its s., rollers being mounted upon a constantlyf driven powenshaft ,76. An electronaignet 77,Whichltcr1n theclutch nr gnct or power magnet, is arranged to mam .ire the driving rollers 7l and 75 to cans them. to attract the iron plate 73. Said/plate is provided with cam. surfaces, so that in the normal posit-ion ol the appinatusthe Asurfzme on one side ci: the aXis 50 will he closer to the driv 'ing Wheel 75 than the surface on the other side of said aXi; is to the driring wheel Nornnllly` thcrelore, when the l "ii-winzig" .not ,is excited the plate T3 u'jill b into engagement with roller to ro )ive naitioii therefrom, and the carrier shalt JO will he rotated in a direction to advance the lnushesu lifter the brushes have been advanced the distance required, the pmvcranugnet will be denergized, the plate 73 will be released from its engagement with driving roller 75, y 4

and said plate will. recover from. its tilted position hy the action of a spring washer 78. "he caln surface of the plate being now angularly displaced from. the axis hf the driving rollers, the body portion. of the plate `will he nearer to the return rollert the magnet is denergized. Springs- (not shown) may be provided as usual for returning the keys to normal position when released'. Each key when depressed is adapted to close two contacts, one controlling' the application of a ground connection to a conductor individual to such key, leading to a corresponding terminal at the loint finder apparatus (Fig. 2) and the ot ier contact beinv adapted to close a circuit common to all t e keys ofthe row. p

Referring now to Fig. 2, the operation of thestepping mechanism and the pointfinder operated thereby will be readily understood. The finder brush 201 is mounted upon an larm extending radially from the central shaft 202, and is adapted as said shaft is rotated to travel over stationary contact terminals 203 which are arran d inthe circular path of travel of said fin er brush. In the form of apparatus shown, the point finder shaft 202 1s adapted t be rotated by ax spring-actuated driving-gear under control of an escapement, the escape.

ment lever 204 being arranged to be vibrated by an electromagnet 205 assaid magnet responds to the intermittent electrical impulses. rl`he shaft 202 carries a ax' wheel 206, which is arranged to be drlven by a gear wheel' 207, which is kept under tension by a coiled spring 2081 One end of the spring 208 is fastened to the gear wheel 207, and the other end of said spring is xed to the plate 209,` which is rotated from time to time in a direction to winjd up the spring. The plate 209 is' carried by a shaft 210, which also carries one member of a friction clutchl adapted to couple said shaft 210 to a constantly driven power-shaft 211. The gear wheel 207 rotates upon, but inde'- pendent of, the shaft 210.

The power-shaft 211 carries an iron driexing roller 213, and the shaft 210 carries an iron plate 212 which is fxedtherete in such a manner that said' plate may be moved flatwise into frietionalI engagement with said driving roller 213 by the action of an elec tromagnet 214 which is arranged to magnetize said driving roller. At the endof eachA complete revolution of the point finder shaft 202, the electromagnet 214 is ,energized to draw the members 212, 213, of the fric tion driving gear into engagement, and thereby cause the shaft 210 to be rotated in a direction to wind upy the spring 208. A

`contact 215 is arranged tobe closed by a cam-lever 216 the end of which rides upon the periphery of said plate, said lever being moved outwardly when the plate 212 leaves its normal restin position; This contact 215 controls a loc l circuit for the electromagnet 214, whereby said magnet may be maintained energized until the plate 212 has :nace ay complete revolution, `gyhereupf'my the escapement.

mageos vibratedf it permitsthe escapement wheel 238 to rotate step by step, thereby rotating the shaft 202 of the point `finder, and advancf ing the finder brush 201 over the series of stationary terminals 203.` ,l

A The stepping impulses, which are received from a distant pointand may be comparatively feeble, need not be required to act directly upon they stepping. magnet to per-V form the mechanical work of operating the i l Preferably a sensitive relay 218 is connected in the, selecting circuit t0 abl receive and respond to the selecting im? 86 directly operates the escapement is connect(- edy in' a local circuit controlled at the frontP co ltact of said stepping relug`- he stationary terminals 2- of theyspointy finder apparatus are arranged iny three divi sions, the terminals in the first division be ing, connected respectively to contactsof cor- A pulses. and the stepping magnet 205 which* y respondin' hundreds keys; the terminals in` a t0- cond the the secon division being connec tacks-of corresponding tens keys, an

terminals in the third division being con' l nected tocontacts of corresponding unita keys. In the apparatus shownthere are at the end of each division two idle terminuls, in addition to the teny terminals con nec'ted to the keys; and there is also at the beginning of ea'el divisioni anextra. terminal, .9*82 or 82 as thel case may be. In the normal starti position s of thedinder brush` 201,l and 1nl the second and third starting' positions s? and s thereof the finder brush lies' o 'ne' step black of the first or zgm` terminal of the corresponding division.V

'The continuity of the stepping circuit shown in heavy lines is controlled Aat the back Contact of a stop relay 219, which i3 connected between the free pole of a group?- Jhbattery `220 and the finder.' brush 20 len the' finder brush in `its advance ovp the terminals 203 reaches the one which been grounde by the corresponding.` key, the stop relay 219' is energized and opens'the- 'selector circuit including the stepping relay 218, whereby the' selecting operation is determined. The stop relay in its `feaponse is also arrangedto close a circlit fur the motor magnet of the sequenceswitch associa-ted with the sender, to advance said se quence-switch to another position in` which another selecting operation may be brought about. The lstop relay 219 is also adapted in its response to close a. local circuit 'iat the stepping magnet 205, including an interrupter. 221, whereby the point finder may: be independentlyV advanced from `the pointf atgwhich it found the terminal l grounded the corresponding key, tothe 224 control the local circuit for the ""jstepping magnet 205, through the inter- "r upter 221, andt'by opening when the finder f brush reaches'a starting point .9.1, s2 or a3, as `the case may he, cause the finder brush to be larrested yin suolistartingv position.

f Mechanism ofi sequcpeetwz'tcwcT-In the {for'ln ofsequenceswitch mechanism shown fin Illix'egs.l 5 to ,Sithej movable member is a L 4cortical rotary shaftc'arrying--a number of itchoperati'n airis', said shaftv being riven. .by power applied he cnstantly:` driven. power-shaft urnes africtin driving 'disk 10'Which .fisda'pted to he` drawn'into" engagement 'fvvithv-nfriction 'rol-lerffQV-carried upon' the shaft?, bythe action "of a.;c1i1tch1magnet12. The roller 9 andthedisk 10` are,o`; iron, and the'motor*I'nagnetj1 2 is `adapted when ex- 'cited to magnetizelsaid ro11e'r.9, which serres 11salrotary` polepiece for said magnet; whereby the drivingdisk is 'attracted into engagement with saidvroller, the rotation of the shaft' 7 thus' continuing as long as the motor magnet-12 remains excited.

l The- 'ca'r'nsv8l carried by the rotary shaft 7 are 'arranged to operate .switch springs 13, forcing 'said springs into engagement with outer contacts 15, or allowing'them to engage their alternate inner'contscts 14, according to the positions V01Es n'idcarns. s many cams and switches mayvbe provided 59 as the particular apparatus tombe controlled r may require. Certain-of the switch 'contacts operated in the successive positions of the movable switch element may-fcon'trol circuits for the motor magnet 12, 'A special switch, such as shown in Fig. '8, isalsopreferahly provided to control a local-circuit for said motor magnet, whereby the initial energizingI circuit Ais bro byjne of the other switches, the inoton eignet may stili be excited by currentqinthelocal circuit until` the next intende`d--,stopping; position of the rotary element is fully reached. is shown in Fig. 6,-tl1e cam. 16 for operating?, the local switch is adapted to he engaged by a cam roller 17 carried hy e pivoter-' he agency Vofl an electromagnetic' switch lever 18. A spring 19 is arranged to act upon said pivotedlever 1S so as to press the cam roller 17 against the edge of the cam i6. When the roiler 17 rides upon a tooth or high part of the cam 1G, said lever lcloses a Contact 20 which controls the iocal circuit for the motor magnet. The teeth of the cani l0 have inclined edges. so that the cam roller l?, after riding over the point of a tooth` is forced doi/yn the opposite slope by the action c' lthe Vspring 19, and thus tends to push against the cam to continue the rotation thereof until the roller 17 reaches the bottom ot the followingr notch. T he rotary element is thus brought to rest accurately in the position where it is intended to stop. lin the operation of tliedevice the circuit Wili iirst be closed for the motor magnet through one of thesprings 13. and one or the other ofthe 4contact anvils 14 or l5 of such spring. Thenas the motor magnetis excited and the shafty of the sequence-switch begins to rotate, the contact through whichk the motor magnet was 1n1- tialiy excited may be hroken. but the local 'circuit will be maintained Ai501' the motor' magnet through the contact 20 closed by the earn 16, 'and the rotary elementwill thus continue to advance until the cam roller 17 reaches the bottom of the next notch of the cam 16. f

inthe diagram, Figs. i. to i inclusive, the. srvitclrsprings of the sequence-switches are not shown in their actuai arrangement, but are so located as 'to `rive the clearest arrange Fio loo

ment of circuits: and the operating cams are not shown. The positions of the rotary element of each sequence-switch 1n which any of its contacts are closed are indicated@ g by `"fnnrnhers placed adjacent to such con@ tarts; each contact being open'in all positions except those indicated by the adiacent numbers. 'For example, contact 409 is closed in the ist or normal position of the seouencesiritch, and in the 2nd and 13th positions thereof, as indicated oy the numbers 1-2-13 placed adjacent. to that contact, and is opened in all other positions. But each seouenceswitch has. a special'contact governingl the local or locking circuit of its motor magnet.- such as contact 20 opfis erated by cam 16 in Fig. 8. As these special y contacts are closed oniy While the rotary element is in transit from one stopping position to the next, the numbers are placed on the side of the switch lever opposite from` the contact, and do not indicate positions in which the contact is closed, hut indicate instead positions in which it is open. Thus, hy reference to the numbers appearing adiacentfto the contact 20h 'of the sequenceswitch of Jthe iii-st selector (Figz) itis` seen that this contact is closed between the ist position and the 3rd., open in the 5rd, closed between the 3rd and the Open lgs flue employed. connected as indicated.

l establshino; the rtall .in the4th. closed between the 4th and 5th, and so on g and that between the 1st and 3rd p L-tioru. and between 'the 3th and 13th posi-- tions. the contat; is continuously closed. The movable element of this sequencesuu- '1 thcrcihire, after leaving; the 1st position, will run through to the 3rd 'Without a stop.; yl' d. upon leaving the Sth position run through to the 13th position witl'xout stop;

{Micra/,Mm of s i/acmfwfk further detailed. description oi? the apparatus used in the system. and. a statement oit the electrical, connections ol each part will beA unnecessary. as devices ot' known types are indi cated ,f the usual conventional symbols, and the electrical connections are clearly shown in the diagram. Certain of the usual appliances required in an actual telephone sys ein., such, for example, as the operators telcplwnc set, are not shown, because their connections and manner of use will he well understood by those skilled in thc art, and

to show them in detail would unnecessarily complicate Vtitle diagram. Several batteries are shown in the diagram, and for convenience 'in tracingr the circuits these are designated by dillcrent-numerals, but it Will ,befunderstood that in practice a single centralhattcry common to the exchange may The orc' nil-ation and inode of operation 'stem can best be understood by tralicilnru the o1. rations or steps involved 1n e.y tendini.,r the connection of a calling line Ll for, transmitting' the neces nur; circuit. and finally disccuincctilnr the'linesand :restoring the apparatus and circuits to normal condition.

fllet it be assumed that subscriber at, tio No. 401 (Fig. desires to conrerse with. the subscriborat station No. 950 (Fig. 4). The `'lling subscribcrsignals the cen tral ollic; .in the 'usual Way by takingr his telephone receiver from its switch hook, by closing the line circuit. and causing lino relay at the central ollice to close a local circuit for the line signal lamp 402. The (mei-atar rec-ponds to `the call by insert ing lier answering plug l403 in the springjack of the calling line and depressing her listening hey' to bring her telephone set (not el'iown) into circuit in .order that she may learn. the number of the subscriber wanted. The insertion of the answering plug. corn-4 plctes the circuit for the cord relay 405, and the, subsequent operrtion ol. the listening key clo which con oletes a'circ'uit 'from battery 408, through the motor ,magnet 407 of the se- 'ouenceswitch associated with the tirst'selector, normally' closed contact 409 o't said sequencc-switch contact 404 of the listening see a spccial""contact 404 thereorav earth. The sequence-switch therefore begins to advance, and by reference to the numerals near the local switch lever 20"; it will be seen that the local circuit for 'the motor magnet 40T remains closed from the tiret position to the third, so that said serpicncc-switch advances to its third position Without stopping. At the second position a contact 411 is closed, controlling a common branch from the supervisory signal lamps 412 and- 413, to earth, whereby said supervisory signal lamps'are brought into service under the control of their respective supervisory relays 414 and 415. As the scqucnce-switch of the first selector reaches the third position, it closes a contact 416 by which a ground connection is applied to the sender lead 418, and a circuit is thereby completed for relay 30() (Fig. 2) which controls the seiaiue of the sending apparatus by thlr` connectinglr circuit which has been put into use. This circuit is traced from battery 301 through the sender-controlling re- .lay 300, to conductor 418, which is multi pled to the contacts 410 of the sequence# switches of all the connecting circuits of an operators posit-ion, the circuithcin completed through the contact 4,16 of tie one which has been taken for use, to earth. In

the same position (3) of the sequence-switch a contact 417 is closed whereby the motor magnet 407 thereof is connected to the sender lead 419, which is adapted to be connected to earth by contact 303 of the sequence-switch associated with the sending apparatus.

The circuit 418 controlled at contact 416.

ciprocal control overv the sequenceswitch of A the first selector. The circuit419 will be closed, as Vwill hereafter appear, when the sender sequence-switch advances to its third position in response to the depression of one oit' the lumdreds lreys. When the relay 300 is excited it closes a circuit from ground llhrougrll the front contact of said relay. contact 30,4 ol? the sender sequence switch,

.th-rough" the motor magnet 317 of said sequence-switch, to the free pole of a grounded battery 316. The sender sequenceswitch therefore moves inunediately to its second position.

. The operator having now communicated 'with the 'calling sullscribcr, and having learned the number of the line wanted. de

j'presses hays (Fig. 1) representing the digits of 'such nur nber. In the case assumed,

aisance i where line No. 950 is called, the operator depresses the hundreds key No. 9, the tens k'ey No. 5, and the units key No. 0. These keys, when depressed, will ground corresponding points in the first, second and third divisions, respectively, of the stationary terminals in the point-finder apparatus. As soon as (ne oit the hundreds keys has been depressed, a circuit is completed for the niftor magnet 317 of the sender seq uenceswitch, through contact 306 thereof, and through the contact 107 of the particular hundreds key which has been depressed (in this casethe 10th key No. ,9) to earth; whereby the sender sequence-switch is advanced from its second to its third position.

In this position the contact 303 is closed, completin the circuit A419 for the motor magnet o the ,sequence-switch associated with the first selector of. the connecting circuit which has been-put into use, whereby said last-mentioned sequence-switch is moved frein its third to its Jfourth position. The sequence-switch of the sender in its 3rd position also closes a cciitact 308 which brings the motor magnet 317 thereof under control of a front contact of the stop relay 219, so that when .said stop relay shall be excited at the end of the` first selecting operation the sender sequence-switch will be advanced fromits 3rd to its L1th position. As socn as the sequence-switch associated with the first selector moves to its 4th positien, a circuit is established by'which the controlling line relay of the -irst selector is energized in series with the stepping relay at the sender. This circuit is as Jtollows: from the :tree pole of grounded battery 421 at the first selector, thrpugh the line relay 420, contacts 4:22 anda/*Y of the sequenceswitch. to sender load 424i, thence through the stepping relay 218 of the sender, (F ig. 2) hack contact 230 of the stop relay 219, through contact' 809 of the .sender sequenceswitch, to earth.

The relay L.120 at the selector, inclosing its front Contact, completes a circuit' from ground, through contact 426 of the sequenceswitch and power magnet 77, to the treepole of grounded battery 425, The power magnet, being thus excited, attracts the tilting disk 73" into engagement with the driv-V ing wheel 75, and the brush-carrying frame of the selector tation being continued as lay 420 remains excited.

y The stepping relay 218 at the 'sender is excited by current in the circuit L124 previously traced,I as soon as the sequence-switch at the iii-st selector closes contacts l22 and 423'. |'this stepping relay 218 closes at its front contact a local circuit from ground, through back contact of armature 229 of the stop relay 219, to the stepping magnet 205, and free pole of grounded battery The long as the line rethe selector .is now is started to rotate, this roarmature of 'the steppir attractive movement, allows f wheel 238 to 'take a hal;

tween said position s1 and tl terminal in the division assi dieds keys. As the brush;

rotated c 1 IX e cani if in a. direction to bring 'tue contf'cL *o against the anvil 86. This complete circuit from Contact 422, 'through wire e back contact the trip magnet spring 91, contact anvil Se, contact poi arm S4, roller 85, segnient 88, aini 92, to earth at llf2-9; thereby dive rent'troin the stepping relay sender and causing said relay t armature. `When the armature of ping relay is retracted it opens cuit of the stepping magnet 5, lows its armature in turn to and so permits the escapeinent iv take another'half step, moving brush 201 to the first or zero teria path.

arcuri lJlien toni of the next notch, the Contact S is opened. breaking theshort oi'cr and permitting the iow of current :i

the stepping relay213.` unless the sto,

219 has in the meantime opened the ping circuit at the sender. as succes impulses are delivered to the stepping relay 218, the selector and the point-linde? at sender are thus advanced in unison step to step, until the tinder hrusli reaches the terminal which has heer by the depressed hundreds key.

grounded terminal is reached,

completed from the free pole battery 220, 2) through 219, to the finder ofrush minal with which it is in cent-acA to ground at the Contact (i.

key which has been depressed.

relay 219 when thus op'n contact 230, thereby hrea circuit 424 which includes the lay 218 at the sender and the line at the selector, the result of a ii to cause one of the 'ten sets t tripped at the'selector, will hereafter be explained. The particular of hrns es which is tripped depends upon the nunihei ofsteps the selector takes in unison with ie ist' point-linder, before said point-linder" es magnet through contact 310 of the sender sequeiice-switch; closes a contact 228 to complete a circuit through contact 308 for the motor magnet 317 of said sequence-switch, whereby the latter is advanced to the fourth position; and closes a contact 232 which completes a circuit for the stepping magnet 205 through contact 223 (operated by the cam on the point-finder shaft) and interrupter 221 to earth. lVlien the local circuit of stepping magnet 205 is thus completed through the interrupter 221, the es- .;iapement is again operated and the finder brush 201 thereby caused to continue its trarel, passing fro'nthe terminal which was grounded by the depressed hundreds key to the next starting'position s2 immediately in advance of the next or tens division of ter- :iiiiuals in the path ofsaid brush.

.in the starting position a2 (and also in the starting position as preliminary to the tliiri'l or units division of terminals) the finder brush 201 rests upon a contact ypiece irliicli is connected directly to battery.

i when the finder brush 201 reaches the seeonil starting position, therefore, the stop .ri/lay' 219, which is connected between the and the finder brush. is short-cirer,H u. When thus released, the stop relay opens contact 228 controlling the local interriipter circuit for the step magnet. opens zifoiitfict 226 controlling its own locking circuit: closes contact 231 to complete a circuit thri'iugh contact 312 of the sequence-switch,

i whereby the latter is moved to its fifth position: and closes contact 230 to reestablish the selecting circuit which includes the stepping relay 218 at the sender and the line relay of the distant selector.

A, numher of dead terminals are provided iii the path of the fiuderbrush 201 between thix last terminal of the division connected to `the hundreds kevs and the starting positfoii s* preliminary to the next division of uiiuals, connected to the tens keys: and lixrwise a number of dead terminals are provided between the last terminal of the teus division and the starting position a picliniiiliary to the u'nits division.'v The spare occupied by these dead terminals is eiiei'gized long enough to permit the brush carrier to travel through a distancel sufficient to trip a set of brushes before saidline relay7- is excited again toshort-circuit the tripr provided for the purpose of securing a tiine magnet, as it will be when the selecting circuit is again closed at the sender.

When the circuit is first established through the line relay 4-20 at the selector to the senden` lead 424, and said line relay by closing at its front contact the local circuit for the power magnet 77 causes the brushcarrier of the selector to `begin its journey, the cam 80 upon the shaft of the selector forces contact spring 81 into engagement with its anvil 82. r1`his completes a circuit from ground through contact 432 of the sequence-switch associated with the selector to the motor magnet 407 of said sequenceu switch, and the free pole of battery 40S; whereby said sequenceswitch is moved from its fourth to its fifth position. The contacts 422 and 423 reinainl'clo'sed in this position, and line relay 420 remains continuously excited 'as lonnr as the circuit 424 is closed through the b k contact 23() of the Stop relay 219 at the sender.

T he short circuit of the line which causes the finder brush at the vsender to take the final half-ste which brings it to the terminal grounde by the depressed units key, is produced by the contact 8G, S7, of the interrupter while the roller 85 is riding up on atooth of the segment S8. New, when the line circuit is opened by the stop relay at the sender, which is energized the moment the finder brush contacts with the grounded terminal, 'the line relay 420 at the selector will be held excited only by current flowing in the circuit controlled by the interrupter contact;- and when said contact is opened as the roller 85 rides down from the i tooth in question into thefollowing notch, the line relay will be released. The result of this will be to cause the trip magnet 67'to be excited totrip a set of brushes, as will presently be described. The provision for releasing the line relay to cause the excitation of the trip magnet only after the openvi ing of a local interruptex,l Contact operated by ,the movable elementf the selector itself insures the accurate timing of the trippng operation, and thusthe accurate selection of the set of brushes to be tripped.

In retracting its armature, the line relayr 420 opens the path previously traced from power magnet 77, through contact 426, to earth, which path is a short circuit about the trip magnet 67. When the armature of the l y ay final selector which is idle. `.55 in lo eration will resenti be described.

,i P P y upon the trip-bar 64, which has been pressed \forivard by the trip magnet 67. The paryicular one of the latch arms 58 to be engaged by a tripping lug will depend upon "ip the num-lier of steps through which the selector'had advanced before the trip magnet was, excited. In the case assumed, where the' hundreds key No. 9 was depressed, the

. selector and the point-finder will have taken my, ten full steps in unison before the release of j @the line relay caused the trip magnet to be lexcited. In those ten steps the latch arms 'l of the lirst nine sets of brushes (counting from the bottom up) had successively passed the` points at which they might havebeen tripped, leaving the latch arm of the t'enth set of brushes in position to be engaged by the projecting lug of the trip bar as the selector continues to advance. The latch arm when engaged by the tripping lug is detained thereby sufliciently to release the 4three brushes normally held by said latch arm, allowing these brushes to be rocked upon their pivots by their springs 54, 55 and 2,5 56,' and so thrust into contact with the grounded metal plate 70. The first selection,

in which the pointfnder of the sending apparatus took ten steps under control of the 10th hundreds keyNo. 9, has thus resulted in bringing into service the 10th set of brushes of the first or hundreds selector, the other brushes remaining out of service.

The set of brushes so selected may now,

by a` further rotary movement of the brush- 5 carrier, be caused to travel over the line terminals in the corresponding row or level.

In the system under consideration, the line terminals in each level of the first selector represent trunk lines leading to final selec- 40 tors of the sameigaoup. ln other Words,

each set of line terni'nals in the 10th lever which has' been isblected represents the lconductors of a trunk line leading to a final selector of thelOth group, which has direct `475 access to the terminala' of subscribers lines .c vnumbered from 900 to 99,9. Any of the nal i `selectors of this hundreds group will serve to complete the desired connection; and after y a set of brushes has been tripped, as before described, the Iirstfseleetcr must therefore 'advance the'selected'setfzof brushes over the correspondin lhorizontal row of trunk line terminals, unil a set is reached representing will be noted that as soon as the tliird or test brush ofthe set which was tripped touchesthe grounded metal plate 70, the line relay 420 is again excited by current from battery 421, through contacts 422 and 463 vof thesequence-switeh to the plates?) ,and the tongue VL56 thereof which bears against the argh of the selected test brush 53, through said brush tothe plate and ground. The :.15 line relay 420 is-thus immediately excited as soon as'4 a set of brushes has been tripped, and again closes at its front contact the short circuit of the trip magnet 67, said trip magnet having been excited only long enough to trip the set of brushes.

The cam is shaped so that when the rotary element of the selector has advanced all the brushes thereof beyond the trip range, the spring 8l Will be contact anvil 83, completing a circuit through contact 433, to the motor magnet of the sequence-switch, Which thereupon moves the 6th position. ln leaving the 5th position the contact i23 is broken, disconnecting the line vrelay 420 from the sender lead 42d; but contact 122 remains fclosed., connectine* said line relay through contact 463 to the third or test brushes 53 of the ten sets lin multiple. As only one set of. brushes has been brought into operative position, the other multiple sets may be disregarded.

The sequencelswtch in leavlng the 5th positions also opens the contact As3() controlling the circuit for the trip magnet 6T,

thus opening the branch by which the power magnet was previously excited in series with the trip magnet, and leaving said power magnet` dependent for its excitation upon current in the circuit controlled at the front contact of the line relay. Said line relay will now govern the further advance of the selector brush in hunting an idle trunk.

The segment 88v of the Selector is provided with a long tooth 89 to be engaged by the roller of its interrupter While the brushes allowed to engage the are passing between. the end of the'trip range andthe beginnm of the range ccntainmv the line termina s. As the brushes pass othe end of the grounded metal seginentythe interrupter roller is passing over theillong tooth 89, and contact 86, 8T, is closed, maintaining the line relay l20 exs cited and the stepping relay 218 short-cir cuited. As the brushes reach the first lset of terminals, however, (in the case of the first selector) and the interrupter contact 8o, 87,is opened, breaking the short circuit 427, and leaving the line relay L20 dependent for its excitation upon a circuit which may be completed through the test brush 53 of the set which has been tripped to atest terminal 63 ofthe -set of terminals upon which the brushes may be resting. If the trunk line represented by the three terminals' upon which the brushes of the selector are resting is busy, the test terminal 63 thereof will be connected to earth, as will hereafter be ei;- plained, but if the trunk line is free, the test terminal 63 thereof will have no such earth connection. A

v As each set of terminals is reached by the brushes, the circuit for the line relav 420 may thereforebe completed through tlie test brush 53 andtest terminal 63 of the trunk line, toearth, if such trunk line is busy endif rae such test circuit is completed the line relay will remain excited and maintain the circuit for the power magnet 77 closed; so that the brush carrier will continue to be' ad?. vanced as long as the brushes are passing over the terminals of lines which are busy. While the test brush is passing from eacn terminal to the next, the circuit for the line relay is closed by the interrupter contact 86, S7. As the test brush reaches each terminal; the circuit for the line relay 420 through the interrupter contact 8G, S7, is broken; and as soon as the test terminal of an idle line is reached, there being no ground connection upon such test terminal, no circuit will exist for the line relay 420, and said relay will be released, breaking the circuit of the power magnet 77, and causing the selector brushes to come to rest upon the terminals of the line so tesi ed and found idle. The line relay 420 in recovering also closes at its back Vcontact a circuit through contact 484 to the motor magnet 407 of thesequence-switch, which is thereb moved from the 6th to the 7th position. n the 7th position the circuits for the test relay andk power magnet of the selector are open, and the sender leadsl 424 and 434 are connected through contacts 436 and 437 to the line brushes 51 and 52, respectively, and so to the conductors 501 and 502 of the trunk line leading to the final selector. Contacts 465 and 464 are also closed, connecting the test brush 53 to earth, and so establishing the grounded or busy condition for all the multiple.test-terminals of the,trunk line selected.

As a result of the first selectingI operation p under control, of the` depresse hundreds key, the circuit has thus been extended through thcrfirst selector to atrunk line terminating in a final selector which has direct access to all the subscribers lines of the hundreds group corresponding lto the numeral of the hundreds key which was depressed. Another selecting operation will now take place under the control of the depressed tens key to cause the chosen final selector to trip the set of brushes which travel over subscribers lines in the desired tens level; after which a third selecting operation will take place under control of the depressed units key, to cause, the tripped set of brushes to advance over the terminals in the mirresponding level to theparticular set connected to the called subscribers line; the finder brush 201 reaches the; starting position s2 and the stop re- --circuited and released, back l stop relay controlling the it closed, but the'steppin till be open at a Contact 311 o uenceswitch. c Contact-309 of' tre-switch, by which the stepping circu closed to earth during the first selection, is opened when the y sequence Ithe arm of said brush, plate 41, contact 436,

of, to the free pole ,x `sequence-switch associated with the final se4 the free pole of battery 316. The Sequenceswitch is thus advanced-to the fifth osiv tion; and in this4 osition a circuit wil be 75 completed for t e motor` ma net 317, y through contact 313 and throng contacts y 108 and 109 of the tens and units ,ke s respectively, to earth, provided a tens ey and a units key has been depressed. Upon the se completion of this circuit the sender sequence-switch will be advanced t0 the 6th` i, position, in which contact 311 controlling the stepping circuit will be closed and the sending apparatus will now be in condition 85 to respond to the next set of step ing impulseswhich will-be transmitted rom the final selector, Fig. 4.

As soon as the brushes of the first selector have come to rest upon the terminals of a trunk line leading to an idle final selector, and the contacts 436 and 437 have been closed, the stepping circuit is established as follows: from battery 504 at the final selector, through the line relay 520 thereof, to trunk line conductor 501 leading back tothe terminal 61 of said trunk line at the first selector, thence through the brush 51 of said trunk selector, spring 54 resting upon sender lead 424 to stepping relay 218 at the sender, through back contact 230 of thc stop relay 219, contact 311 of the sender sequence-switch to the other sender lead 434, thence through contact 437 at the first selector, to plate 42, tongue 55 and brush 52 thereof, to terminal 02 of the trunk line,

conductor 502 of said trunk line, through the normally closed contact 505v of the Se ,f quence-switch associated with the fnalse.- lector. .v i

The line relay 520 'of the final selector corresponds generally to the relay 420 of j the first selector. When excited by current .in the circuit just traced it closes at ,itsln front contact a circuit from ground throughi the normally closed contact 508 of the se-T quence-switch and motor magnet 507 therefff" of battery 50G. The

lector is thus moved to itsirsecond postioniy in which'contact `526is closed, whereby the line relay 520, remaining excited,closes a', circuit from ground throughits front con: tact and contact 526 of the sequence-switch; 125 through the agency of power magnet 77 of thefinalselector, to the free pole ofjnitter 525. The power magnet being thus excite the brush carrier is started in rotation, and,

as,` the inter-capter roller passes over iilso tot" coothedscgment it naires and breaks the contact 556, Si', estab'lshing; at each closure of contact a short circuit of the line, i l 520 to conductor 52T, con- .enceeswitcln back conniagnct GT of the final the interrupter Contact "ne stepping relay 21S at nergized each time such 1o 1 iort circuit the inal selector is closed.

is the lnush carrier ot trie iinal selector begins to rot ci, the cuni S of said linal selector iorces che spring Sl into engagement with the conta t anvil S2, completing a circuit to ground throngh said Contact 82 and contact 532 of the seznience-switch assorciated with the final selector, to the motor w magnet 507 oit said sequence-switch and the 'ir-ce of grounded battery 506. rlhe sean-fA e-switch is thns moved to the third position, in which a set of brushes may be tripned.

in the l ecting; ycircuit is established, connecting thc Vline relay of the final selector and the stepping relay Q18 of the sender in series, said stepping relay 2l8 at each impulse received 'from the selector completes .y 'the loc-'al circuit Afor the step magnet 205, and the escapcinent the point 'lnder apl 3c paratns is operated as before described, now nlvai'ieing'the iinzer brush 201' over theY t 1 iinals in the second ortens division. l en the finder brush 201 in its advance lflics the terminal which has been nded by the depressed tens-key, (in this verminal no 5l, the stop relay 219 is l. before. and opens lts back con tact 2,950- controlling' the stepping circuit.`

also clos-es its own local contact 926, closes contact c circuit for the motor mag'- net of the sender meme-switch, whereby the latter is moved from the 6th to the Tth position, and close contact 232 to complete the local circuit tor step magnet 205, thro'lgh the interrnpter 221. The finder brush is therefore moved to the third starting' position the stop relay remaining excited until said position is reached, wlwrenpon .said stop relay is short-circuited as betere described, The stop relay inrecoverine opens its lockinnjfcircuit at contact q98; opens the i `terrupter circuit at contact Said stop relayv locking' circuit at XMS to complete a z r2: closes contact-Qdi to'complete ad circuit YFor the motor mae'nct or the sequencesvfitcln whereby the latter is moved from its: swcnth to its eiqhth position; Iand closes '-1, contuct'QSO to reestablish the selecting circuit l.V 4:34 to await the next set of selectinfr impulses to be received 'from the final thepoint grounded by the depressed tens key. ln retracting its armature said line relay opens the short circuit of the trip magnet 67, leaving a circuit established from battery 525, through power magnet 77, trip magnet 6,7, Contact 530 of the sequenceswitch, and back contact 551 of the testrelay 550, to earth.`

The operation of tripping a setl of brushes is the same as previously described with reference to the first selector. The particular set of brushes to be tripped is de` pendent upon the particular tens key which was depressed. rlhat is to say, in the case assumed, AWhere the tens key No. was depressed, the brush carrier of the final se.l lector will take six steps (corresponding to the siX steps oi the point inder from position ,s2 to the sixth terminal No. 5 in the tens division on the point finder apparatus) before the trip magnet is excited, whereby the sixth set of brushes (counting from the bottom up) will be tripped. The sixth tens terminal in the bank of line terminals on the final selector has thus been chosen. There are ten setso'f line terminals in this level, representing the subscribers lines Nos. 950 to 959 inclusive. The iinal selection, under control oi" the units key, will determine the particular set of line terminals upon which the selector brushes will be brought to rest.

When the test-brush 53 of the set which is tripped nmlies Contact with the grounded metallic segment l0 of the selector, a circuit` is completed from battery 504, through the line relay 520, to contact 538 oi' the sequence`v switch, test brush 53, segment and earth Thisvmaintains the short circuit of the portion ot theline leading back to the sender,

and also causes the line relay at the selector llf,

87. When all the brushes oi the final se lector have passed the trip range, 'the cam allows the Contact 83 to be closed, corn plating a circuit for the motor magnet 50T, of the sequence-switch associated with the nal selector. whereby said switch is moved from the 3rdv to the fifth position. ln this position the trip magnet is permanently cut out of circuit by the opening of Contact 530.

ln the final selector, 'the segment 88 is provided with an extra notch in advance of the notches corresponding* to the positions in which the brushes rest upon the line terminals. As the interrnpter roller Se of the nal selector passes down from the long tooth into this first notch in advance of the notches corresponding to line connecting positions, the short circuit controlled by the interrupter contact 86 is broken, and the first of the new series of selecting impulses is applied to the stepping magnet'218 at the sender. i

.The back contact 230 of the stop relay 219 at the sender having been closed when the finder brush reached the third starting position s, the selecting circuit is completed at the sender to await the first of the units selecting impulses to be receivedfrom the final selector. The stepping relay 218 in responding to the first impulse transmitted when the interrupter roller of the final selector enters the first notch following the long tooth 89 of the toothed segment, causes the stepping relay to complete the local circuit for the step magnet 205, whereby the finderfbrush 201 is advanced a' hall? step. ,Now as the interrupter roller 'at theifinal ,selector rides up' on the neiittooth,U and short-circuits the stepping relay at the sender, the localcircuit of the' stop magnet 205 is opened, and permits the Yescapement to take another half step, advancing the finder brush 201 tothe first or zero terminal in the division of terminals which are connected to the units keys.

As stepping impulses are `delivered from the final selector to the stepping relay 218 at thesender, the finder brush 201 may thus be advanced overvthe row of terminals in the third division until a terminal is reached which has been grounded by the corresponding units key. In the caseassumed, where line No'. 950 was called, and units keyNo. 0 was depressed, the first or 0 termina in the third division will be grounded, and the finder brush 201. after having taken the two half steps from. position as to the irst or zero terminal, will complete atsaid terminal a circuit for the stop relay 219 which will operate as before to open the stepping circuit at contact 230. l f

Now as'the interrupter roller S5 at the final selector enters the second notch after the long tooth 89, (that is, 1 v if corresponding to a position brushes rest upon line termi circuit527 will be broken at ptet Contact 86, 87. As the stop rciaI :i at the sender has already been excited, due to the fact that thefirst or 0 units key has been depressed, no circuit will exist for the line relay 520 at the final selector when the interrupter contact 86, 87, is broken, and said line relay will be denergized. The circuit :for power magnet 77 will thus be broken iin. av 520 i 'i its front conie will cease having of line rot e, been brought to restA4 said sequence-switch is advanced from the.

8th to the 14th position, the contact 20 controlling the local circuit for the motor magnet of 'said switch being continuously closed until the 14th position is reached.I

The stpp relay 219 also closes at contact`220 a locking circuit for its own winding, and closes at the front contact of armature 229 the local circuit for the step magnet 205, .i

through the interrupter 221. The finder brush 201 therefore begins its onward journey around to the starting point s1.

When theA sender sequence-switch reaches the 10th position, the contact 303 is closed, and remains closed in the 10th, 11th and 12th positions. This contact 303 completes a circuit from ground to the sender lead 419, through the contact 417 of the sequenceswitclnassociated with the first selector, and through the motor magnet 407 of said sequence-switch to the free pole of battery 408. ,The last mentioned sequence-switch therefore advances to the 8th position. 1n this position the sender leads 424 and 434 cut oi from the operators connectin circuit by the opening of contacts 436 an 437;

are

and contacts 4461 and 462 are closed, uniting the main conductors of the connecting cir cuit from the answering plug 403 to the brushes '51 and 52 of the first selector, and over the circuit which has been established to the final selector, the brushes whereof pow rest upon the terminals. Jthe called When the sender sequence-switcli leaves its 12th position, the contact 321A is opened, therebyV breaking the circuit of the locking n-iiuriis 1.02 of all the keys, thereby permittint, the lieve which were depressed to be rcturneil to their normal positions.

:M the sonder sequence-switch reaches the iih position, a contact 322 is closed, complating a circuit from battery 235, through the power magnet 214 of the mechanism which winds up the spring 208 of the point finder apparatus. The magnet 214 when excited attracts the iron plate 212 into engagement with the driving roller 213, whereby said plate wind up the spring 208. begins to rotate, the cam thereby closes contact 215, which maintains the circuit of the power magnet 214 until 

